"""
在视图函数中
    自定义的分页组件，以后如果想要使用这个分页组件，你需要做以下几件事
    1.根据自己的情况去筛选自己的数据
    queryset = models.PrettyNum.objects.all()
    2.实例化分页对象
    page_object = Pagination(request, queryset,search_data=search_data)
    context ={
            "search_data": search_data, 查找条件
            "page_queryset":page_object.page_queryset,分完后的数据
             "page_string": page_object.html() 生成的页码
        }
    return render(request, "pretty_list.html", context)
在HTML页面中
{% for item in page_queryset %}
{{item.属性}}
{% endfor %}

<ul class="pagination" style="float: left">
    {{ page_string }}
</ul>

"""
from django.utils.safestring import mark_safe

class Pagination(object):
    def __init__(self, request, queryset, page_size=10, page_param="page", plus=5):
        """
        :param request: 请求的对象
        :param queryset: 符合条件的数据
        :param page_size: 每页显示多少条数据
        :param page_param: 在URL中传递的获取分页的参数 ，例如/pretty/list/?page=12
        :param plus: 显示当前页的前几页或者后几页
        :param search_data: HTML中返回的搜索条件
        """
        import copy
        query_dict = copy.deepcopy(request.GET)
        query_dict._mutable = True
        self.query_dict = query_dict
        self.page_param = page_param
        page = request.GET.get(page_param, "1")
        if page.isdecimal():
            page = int(page)
        else:
            page = 1
        self.page = int(page)
        self.page_size = page_size

        self.start = (page - 1) * page_size
        self.end = page * page_size
        self.page_queryset = queryset[self.start:self.end]
        total_count = queryset.count()
        total_page_count, div = divmod(total_count, page_size)
        if div:
            total_page_count += 1
        self.total_page_count = total_page_count
        self.plus = plus

    def html(self):
        if self.total_page_count <= 2 * self.plus + 1:
            # 数据库中数据比较少<2*plus+1
            start_page = 1
            end_page = self.total_page_count
        else:
            # 数据库中数据比较多>2*plus+1
            # 当前页<5时
            if self.page <= self.plus:
                start_page = 1
                end_page = 2 * self.plus + 1
            else:
                # 当前页>5
                # 当前页+5 >总页面
                if (self.page + self.plus) > self.total_page_count:
                    start_page = self.total_page_count - 2 * self.plus
                    end_page = self.total_page_count
                else:
                    start_page = self.page - self.plus
                    end_page = self.page + self.plus
        # 页码
        page_str_list = []

        self.query_dict.setlist(self.page_param, [1])
        # 首页
        page_str_list.append('<li><a href="?{}">首页</a></li>'.format(self.query_dict.urlencode()))
        # 上一页
        if self.page > 1:
            self.query_dict.setlist(self.page_param, [self.page-1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
            page_str_list.append(prev)
        else:
            self.query_dict.setlist(self.page_param, [1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
            page_str_list.append(prev)

        for i in range(start_page, end_page + 1):
            if i == self.page:
                self.query_dict.setlist(self.page_param, [i])
                ele = '<li class ="active"><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            else:
                self.query_dict.setlist(self.page_param, [i])
                ele = '<li><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            page_str_list.append(ele)
        # 下一页
        if self.page < self.total_page_count:
            self.query_dict.setlist(self.page_param, [self.page + 1])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
            page_str_list.append(prev)
        else:
            self.query_dict.setlist(self.page_param, [self.total_page_count])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
            page_str_list.append(prev)
        # 尾页
        self.query_dict.setlist(self.page_param, [self.total_page_count])
        page_str_list.append(
            '<li><a href="?{}">尾页</a></li>'.format(self.query_dict.urlencode()))
        search_string = """
        <li>
        <form method="get" style="float: left;margin-left:-1px" >
                    <div class="input-group" style="width: 200px">
                        <input type="text" class="form-control" name="page" placeholder="页码"
                        style="position: relative; float: left; display: inline-block; width: 80px;border-radius: 0"/>
                <button class="btn btn-default" type="submit" style="border-radius: 0">跳转</button>
                    </div>
                </form>
        </li>
        """

        page_str_list.append(search_string)
        page_string = mark_safe("".join(page_str_list))
        return page_string
